Electronic devices which are widely used as necessities or commodities in today, such as cellular phones, MP3 players, MD players, notebook computers, portable radios, digital cameras, and camcorders, are supplied with power from storage batteries or dry batteries. However, these batteries have to be recharged or exchanged into new ones after a definite period of time. A user has to have access to a power source or auxiliary power supply to recharge a storage battery, but he/she may not recharge the storage battery if he/she is remote from a power source or has no charger.
To solve such problems, portable solar cell electricity chargers have been developed. For example, the U.S. Pat. No. 5,898,932, Zurlo et al. (FIG. 1), and Korean Patent Publication No. 2003-0053988 (FIG. 2) disclose technologies of attaching directly a solar cell plate to the backside of a storage battery for a cellular phone. However, those approaches have a problem that the solar cell module attached to a cellular phone can be used for only the cellular phone and is not compatible with other portable electric devices.
The U.S. Pat. No. 5,522,943, Spencer et al. (FIG. 3) and U.S. Pat. No. 6,476,311, Lee et al. (FIG. 4) disclose a solar cell charger built in a separate portable case. However, such a solar cell charger built in the case may not supply enough power for electric devices because the surface area of the solar cell plate to absorb sunlight is narrower as portable electric devices become smaller and lighter. In addition, the solar cell charger built in a portable case has not presented a concrete technology for automatic voltage regulation to provide an adaptive voltage to diverse electric devices adopting a different power voltage respectively.
In the mean time, a conventional solar cell charger has no means to adjust and position the angle of a solar cell plate to absorb the available light in the most efficient fashion, i.e. aligning the solar cell plate perpendicular to the irradiating line of given light. Moreover, it is very difficult to provide the solar cell electricity charger with appropriate aligning & positioning structure in a mobile environment.
In addition, a charger has to have means of bipolar recharging operation, which enables a connecting terminal to freely change its polarities, because electronic devices with fixed polarity connecting terminal are very inconvenient to use in a mobile environment. However, the conventional solar cell charger requires polarity matching for recharging operation.